Interval Data Tab

The following data can be entered on the Interval Data tab:

Top Depth: This is the top depth of the depth interval. The set of depth intervals should cover the entire thickness of the model. If the Time Varying Properties feature has also been selected, this will be the top depth for the selected interval and time period.

Bottom Depth: This is the bottom depth of the depth interval. The set of depth intervals should cover the entire thickness of the model. If the Time Varying Properties feature has also been selected, this will be the bottom depth for the selected interval and time period.

Darcy Velocity: This is the Darcy Velocity for the depth interval. A negative value indicates an upward flow or flow in towards the source. If the Time Varying Properties feature has also been selected, this will be the Darcy velocity for the selected interval and time period.

Note: When using both the Variable Properties option and the Passive Sink option, the Darcy velocity used is the product of the Darcy velocity specified in both of the options. For clarity, it is recommended the user specify the Darcy velocity on the Variable Properties option as 1, and vary the Sink Darcy velocity.

Rate of Removal: This is the rate of removal of contaminant by the passive sink. If the Time Varying Properties feature has also been selected, this will be the Rate of Removal for the selected interval and time period. According to the principle of continuity of flow the rate of removal should be equal to:

R_r = (v_a1 - v_a2) L / h

where,

Rr = Rate of removal or outflow velocity (flow per unit area per unit time),

va1 = Darcy velocity above the interval,

va2 = Darcy velocity below the interval,

L  = Landfill length,

h  = thickness of the layer from which fluid is being removed.

An example would be a 600 m (L) long landfill with a 0.3 m thick (h) secondary leachate collection system. The Darcy velocity above the secondary leachate collection system is 0.01 m/a (v_a1), and below is 0.003 m/a (v_a2). The rate of removal is then:

R_r = (0.01 - 0.003) * 600 / 0.3 = 14 m³/a/m² = 14 m/a

Rate of Inflow: If the Inflow Rate option has been selected on the previous tab, the Rate of Inflow field will be shown. This is the rate of inflow into the passive sink. If the Time Varying Properties feature has also been selected, this will be the Rate of Inflow for the selected interval and time period.

Phase Parameter: If the Phase Change option has been selected on the previous tab, the Phase Parameter field will be shown. This is a dimensionless phase parameter as discussed i n Chapter 2. If the Time Varying Properties feature has also been selected, this will be the Phase Parameter for the selected interval and time period.